Acid inhibitors



Pa tenteclApr. 12, 1949 ACID INHIBITORS Har'old RFS-lagh; Midland,Mich., assignor to--Tlie I Dow-' CIiemical- G'ompany, Midland, Michz; a:

corporation of Delaware N'orDrawing. Application July. 29, 1944,S'erial'No. 547,309

fiiom' oal" tar; and mercaptans; inhibitor; to

be o-f vahieishouldbe available atlow cost and efiectivein lowconcentrations; For certain pur=- poses, e. g. in acidizing deep Wells,it often is important that the inhibitor be effective at hightemperatures. Also, for many purposes it; should.

not be unduly poisonoua'or"obnoxiousto handliezx. Most of the acid.inhibitorsherritofdresavailable.

commercially are deficient..-in.one.i or: more of 5 I these respects.

I have found that liquidproducts'resultingfrom:

the reaction of elementalsulfur at elevated tem-- peratures withunsaturated hydrocarbons containing at least six carbon atoms in -themolecule as well as substances obtained byethe oxidation= of thesereaction 'products are v'ery effective inhibitors of theactionotnon-oxidizing mineralacids on ferrous metals and are effectiveat higher temperatures than. are the inhibitors. heretofore available,even when usedl'in smallamounts.

A'sjust stated; certain. ofithese new inhibitors are-prepared b'y heatingsthe unsaturated hydrocarbons with elemental sulfur, avprocess hereindesignated as sulfurization, the resultin prod.- ucts being designatedas sulfurized unsaturated hydrocarbons. Others-of the new'inhibitors are40 obtained by. oxidizing the sulfurizedunsaturated hydrocarbons, e.g.,by:means 'otinitric acid, and are, by way: of convenience, hereinreferred to as. oxidized'sulfurized unsaturated hydrocarbons or simplyas oxidation products of sulfurized unsat urated hydrocarbonsz Thesulfurization is usually carried out to obtainl'iquid "products byheating, the unsaturated hydrocarbons or mixtures of. the samewithlfromh.

about 0.5' to about 4,0"molecular. proportions of 5 sulfur for from one:to sixteen hours at temperatures between. 100 and 250". C. The reactiontemperature and time dependgupon the ease with which the particularreactionninvolved." takes place. The reaction is carried'outconveniently A great 10 irran autoclave, preferabliywith agitation.Larger proportions of sulfur; higher: temperatures;-.or:" 31;.

longer period 'of heating mayrbe' employed zifides sired, although underthese conditions; the products tend to be viscousvoilsnor: even.resinous solids: and as such are :notas readilyaemployedias; whenprepared as indicated above; Smaller?- proper-:- tions-of sulfur andIBSSASBYBI'E reaction conditions: may also be employedif desired,although" under: these conditions the maximuminhibiting: action: ofthelproduct' may: not be: developed. Durin -the course: of the.reactionchydrogen: sulfide .mayv be; evolved; particularlytiftmore thanonemolecu'lan" proportion of sulfur isausedz The-pressureon-therautoclavemay bereIieyeditrom.timeltoztime-byree leasingtheaccumulatedhydrogemsuliide'ia; Whom. prepared under the preferred conditions; the:furized unsaturated hydrocarbons are dark coloreddiquids only slightlysoluble in water and having, usually, a specific gravity somewhatgreater than that of water. Little is known of thea-compositionof. theseproducts. other than that they contain between about 15' and 35 percent,usually between about 20 and about 30 per cent,- of -s-ulfu-r. They aresoluble-in a numberrof. organic solvents, such as carbontetraehloride;-. acetone, acetic acid, and kerosenec The oxidation. ofthes sulifurized unsaturated, hydrocarbons may be carried outconveniently; by dissolving the. sulfurized product in annor-w ganicsolventwhich. is. not. easily oxidized, such as carbon tetrachloride,acetic acid, ethylenedichloride, or kerosene, and then treatin thesolution with fromoneto two molecular proportions of an-oxidizing agent,such as aqueous nitric acid or" aqueous chromic acid; at somewhatelevated temperatures, e. g. at from 50to 'C'. The mixture shouldbeagitated-duringthe addition of the oxidizing agent; Upontermination ofthe oxidation, the solution of the oxidation productin the organicsolventmay-be-used directly as aninhibitor, if desired, or the solventmay beremoved-by vaporization-under vacuum to obtain the oxidation;product substantially undiluted with a solvent. The -oXidati0n-may,-"in=some instances, be-carried out'without the" aid of a solventfor thesulfurizedunsaturated hydrocarbon although, in this instance,considerable tar for-' mation usually'occurs. For this-reason, theuse ofa solvent'is preferred; Little is known-of the composition of the,oxidation" products. Their solubility characteristicsare similarto thoseof the unoxidizedsulfurized products; The specific gravity is usuallyincreased somewhatduring-the oxidation and" the percentage of sulfurinthe compound is usually decreased to some extent. The oxygen contentof the oxidized product is usually from about 3 to about per cent.Analyses of the oxidation products by means of infrared absorptionspectra show them to contain little or no compounds containingsulfoxicle radicals. Generally speaking, the oxidation products aresomewhat better inhibitors than are the sulfurized compounds from whichthey are prepared.

Among the sulfurized unsaturated hydrocarbons which, together with theiroxidation prodducts, are particularly eifective as acid inhibitors arethose obtained from cyclohexene, methylcyclohexene,3-cyclohexyl-cyclohexene, dipentene, alpha pinene and turpentine oil.Other sulfurized unsaturated hydrocarbons which also have inhibitingproperties, although somewhat less efiective than those noted above, areobtained by sulfurizing such unsaturated hydrocarbons as3-phenyl-cyclohexene, styrene, diisobutylene, triisobutylene, ahigh-boiling unsaturated portion of a naphtha base petroleum, referredto commercially as naphthenic oil, and a high boiling unsaturatedfraction isolated from the mixture obtained by cracking kerosene or fueloil, said fraction, herein designated as alkylene oil, having a specificgravity of about 0.981 at C. and boiling over the range 111 to 113 C. at150 mm. pressure.

Table No; 1, which follows, illustrates the properties of, and thereaction conditions for, the preparation of several representativesulfurized unsaturated hydrocarbons characterized by their higheffectiveness as acid inhibitors. Others unsaturated hydrocarbons may besulfurized readily in the same general manner.

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tone, kerosene, and a number of other organic solvents. Infraredabsorption spectra of the product showed it to be substantially free ofcompounds having the sulfoxide radical.

When used as acid inhibitors, the sulfurized unsaturated hydrocarbons ortheir oxidation products are simply added to the aqueous nonoxidizingmineral acid, e. g. hydrochloric, sulfuric, or phosphoric acid, at anytime prior to its use. Although the degree of inhibition is dependent tosome extent upon the amount of inhibitor present and upon theeffectiveness of the individual inhibitor used, nearly completeinhibition of the reaction of aqueous non-oxidizing mineral acids withferrous metals may be accomplished by the addition of less than 2.0 percent, and usually less than 1.0 per cent, of the inhibitor based uponthe weight of the aqueous acid. In many instances the inhibitor iseffective at concentrations as low as 0.2 per cent. Slight agitation ofthe mixture of acid and inhibitor is desirable, although not essential,since in use the mixture will ordinarily be agitated sufficiently. Theundissolved portion of the oily inhibitor is thus dispersed throughoutthe body of the liquid and tends to remain in this desirable condition,particularly when the specific gravity of the inhibitor and the aqueousacid are approximately equal.

These new inhibitors are particularly valuable since they are eifective,not only at ordinary temperatures, but at temperatures as high as 200 F.This efiectiveness at higher temperatures is of great advantage since itallows well treating, pickling and other cleaning operations with acidsto be carried out at higher temperatures than is possible with otherinhibitors, thus shortening TABLE N0. 1

Reaction Properties of Conditions Mols S Product Unsaturated HydrocarbonSulfurlzed {fifif Temp. Time carbon Sp. Gr. at Percent 0.) (hrs) C. S

Cyclohexene 185 12 1 l. 070 28. 01 3-Vinyl-Cycloliexene 175 12 1 1. 08422. 01 Methyl-Oyclohexene 185 12 l 1. 058 25 Turpentine Oil (Approx.Empirical forumla CmH 200 4 2. 68 1. 1165 29. 15 Dipentene 175 10 2 l.067 27. 42 Alkylene Oil 145 l. 5 l 0.6 1. 169 24. 25 Styrene 155 3. 5 1l. 142 23. 95

1 Approximate.

The oxidation of the sulfurization product of turpentine is illustrativeof the general manner in which oxidation products of other sulfurizedunsaturated hydrocarbons may be prepared. Thus 200 grams of thesulfurization product of turpentine having a specific gravity of 1.1165and a sulfur content of 29.15 per cent was dissolved in 110 grams ofethylene dichloride and heated to 70 C. with stirring. 80 grams of percent aqueous nitric acid was added over a period of one-half hour at atemperature of 75-80 C. Cooling was required to remove the heat ofreaction and brown fumes were evolved from the mixture. After heatingfor an additional one-half hour at 75 0., the mixture was allowed tostand and the aqueous layer which separated was discarded. 285 grams ofoily solution were obtained. The product, after removal of the ethylenechloride by evaporation under vacuum, contained 20.42 per cent of sulfurand 5.8 per cent of oxygen. It was a thick dark oil insoluble in waterand soluble in ethylene dichloride, carbon tetrachloride, acetic acid,aceinstances permitting attack by the acid of undesirable substanceswhich are not attacked at lower temperatures. Other mineral acids of anon-oxidizing character in addition to those mentioned, as well as acidreacting salts, such as sodium hydrogen sulfate, calcium chloride, andthe like may be similarly inhibited.

Certain advantages of the invention will be seen from the followingexample, which is illus trative and not to be construed as limiting theinvention.

tiveness of a number of acid inhibitors prepared by sulfurizingunsaturated hydrocarbons and by oxidizing certain of the sulfurizedunsaturated hydrocarbons. The results of these tests are summarized inthe following Tabe No. 2. In conducting each test, milliliters of anaqueous acid of the indicated composition and concen;

5, tration, togethen-withthe indicated amount of the inhibitor named,were placed in an erlenmeyer fla'slc A strip of mild steel measuringapproximately 2% inches by 1 inch by -%;inch and weighingapproximately-47 grams=waszcarefully cleaned to remove all rust anddirt, dried, weighed accurately; and totally immersed in the aqueousacid in the flask. The-flask was covered-loosely with a watch glass andmaintained at the indicated-temperaturefor the length" of time noted.The" stripofmild-steel' wasthen removed, washed with distilled water,dried andthe loss in weight duetQa-ttack of the acid onth'e metaldetermined bytjreweighing'. The loss in weight in pounds; per day persquare foot of surface-was calculated.

2. A composition-comprising an. aqueous nonoxidizing mineralacids'olution' and'a liquid sul' fur-ized hydrocarbon formed by directreaction of sulfur with an olefinic hydrocarbon having atlea-stsixcarbon atoms'in the molecule, which sulphurized hydrocarboncontains between and '85-percent by weight-oi chemically combinedsulphur.

3'. A composition comprising an aqueous nonoxidiz-ihgmineralacidsolution and a liquid product prepared icy-heating, attemperaturebetween 100 and 250" C2, sulfur together with an olefinichydroc-arbonvhaving at least six carbon. atoms in the" -molecul'e, whichsulplhurized hydrocarboni V 15 containsbetween 1-5 and per cent byweight of 'ihis value was compared w1th-the corresponding y binewsulhur. value obtained'ina duplicate-determination-car- 21'; A compositioncomprising an aqueous-non ed ut und r s a l si t omitting oxidizingmineral' acid' solution and a liquid prodthe inhib tor; From the valuesobtained-in' 'th'ese t; preparedlby heating one molegular pfopor;comparatlvei i t s, the percentage ef tion o'f an olefinichydrocarbonhaving at least fect1veness of; themhibiton was calculated in a(!- six ca rbgn to -4 mm 11101601119 together; ith cordance with the equation: fr0150x0 molecular proportions of i sulfur 100 L for f'rom' l to lfi''hours at a temperature between Eifect1vcness=- 100 and*250-'C.'

u 25 5. A composition comprising an aqueous nonwherein Lu isthe loss. inweight of the metal oxidizing mineral 'acidsolutionand a relativelystnpin'the uninhibited andzLiis the'lossin weight small proportion of aliquid product prepared by of the str1p in the inhibited acid. heatingone-"molecular: proportion of an oleflnic TABLE No. 2

Per cent Per cent Inh1b1tor Acid Expo- Less 111 Wt. of Loss in Wt. ofPer cent Inhibitor Used t s Used sure Time Test Strip, Check Strip,Effectiveness Aquzmus and (hours) IbsJday/sq. ft. lbs./day/sq. ft. ofInhibitor Add) Cone.

Slaliurized 3-Vinyl-0yclo 5 H01 exene 0. 2 150 10 0. 2a .418 04. 0 Suliurlzed Methyl-Cyclo- 1 15 Ho 0 exene .0 l 150 16 4 SulfurlzedTurpentine O 337 1 M 10 o o 0. 2 5 H01 150 15 .0050 0. 41s 97. 7 0. s 5H01 150 10 .0009 0. 41s 97. 5 0. 5 15 E01 150 10 0. 041 1. 025 05. 0 0.4 15 H0] 175 15 0. 004 1. 42 05. 5 0. 5 15 E01 175 10 0. 051 1. 42 90. 50.4 15112801 175 10 0.023 0.938 07.5 0.5 15 H7507 175 15 0. 0285 0.05897.0 0.4 15117104 175 15 0.0275 0.435 04.0 0.5 15 H3PO4 175 10 0.017 0.435 90.0 0. 2 5 H01 150 16 0. 01s 0. 400 05. 5 0. a 5 H01 150 15 0. 0120. 400 07. 0 0. 5 15 E01 150 10 0.085 0.895 00. 5 0. 2 5 H0] 150 10 0.002 0. 390 04. 5

'ri pennne 12 E 1 is 0. 0318 1.38 07.7 0 00 6 9 .2 Suliurized andoxidized 0 0165 o 435 6 Dipentene 0.2 5 H01 200 16 0. 0085 0. 425 98. 0

Other modes ofapplying the principle of the invention may be employedinstead of those explained, change being made as regards the materialsemployed, provided the ingredients stated by any of the following claimsor the equivalent of such stated ingredients be employed.

I therefore particularly point out and distinctly claim as my invention:

1. A composition comprising an aqueous nonoxidizing mineral acidsolution and a liquid product selected from the class consisting ofliquid sulfurized hydrocarbons formed by a direct reaction of sulphurwitlh olefinic hydrocarbons having at least six carbon atoms in themolecule which sulphurized hydrocarbons contain between about 15 andabout 35 per cent by weight of chemically combined sulphur, and liquidproducts resulting from incomplete oxidation of said sulphurizedhydrocarbons, which incompletely oxidized liquid products containbetween about 3 and about 10 per cent by weight of chemically combinedoxygen.

hydrocarbon having at least six carbon atoms in the molecule togetherwith from 0.75 to 4.0 molecular proportions of sulfur for from 1 to 16hours at a temperature between and 250 C.

6. A composition comprising an aqueous hydrogen halide solution and arelatively small proportion of a liquid sulfurized hydrocarbon formed bydirect reaction of sulfur with an olefinic hydrocarbon having at leastsix carbon atoms in the molecule, which sulphurized hydrocarbon containsbetween 15 and 35 per cent by weight of. chemically combined sulphur.

7. A composition comprising an aqueous hydrochloric acid solution and arelatively small proportion of a liquid sulfurized hydrocarbon formed bydirect reaction of sulfur with an olefinic hydrocarbon having at leastsix carbon atoms in the molecule, which sulphurized hydrocarbon containsbetween 15 and 35 per cent by weight of chemically combined sulphur.

8. A composition comprising an aqueous hydro chloric acid solution and arelatively small proace-met portion of a liquid product,containingbetween 15 and 35 per cent by weight of chemically combined reaction ofsulphur with turpentine oil;

9. A composition comprising an aqueous hydrosulphur, which liquidproductis formed Icy-direct chloric acid solution and a relatively smallproportion of a liquid product, containing between 15 and 35 per cent byweight of chemically combined reaction of sulphur with vinylcyclohexene.

10. The process for reducing the corrosive ac- -l tion of an aqueousnon-oxidizing mineral acid 1 sulphur, which liquid product is formed bydirect a 1 -10 solution on a ferrous metal, which comprisesincorporating with the aqueous non-oxidizing mineral acidsolution aliquid product selected Iromthe class consisting of liquidsulfurizedhydro carbons formed by a direct reaction of sulfur witholefinic hydrocarbons having at least six carbon atoms in the molecule,-whicl'isulphurized i hydrocarbons contain between about 15 and about 35per cent by weight of chemically combined sulphur, and liquid productsresulting from in I complete oxidation of said sulphurized hydrocarbons,which incompletely oxidized liquid products contain between about-3 andabout 10- per cent by weight of chemically combined oxygen.

HAROLD R. sLAGI-L REFERENCES CITEDn t The following references are ofrecordin the file of this patent:

UNITED STATES PATENTS p REFERENCES Glass et aL, Chemical Abstracts,vol.- 24, p; 87; (1930). I

- Nakatsuchi, Chemical Abstracts: vol. 25, p. 938,

Ellis, The Chemistry of Synthetic Resins, vol.

- 1, p. 280, ReinholdPuhCo; sNewYcrk (1935).

